CAUSE OR CONSEQUENCE? WILDFIRES AT THE TRIASSIC-JURASSIC AND CRETACEOUS-PALEOGENE BOUNDARIES

The Earth underwent dramatic changes during the transition from the Triassic to the Jurassic (Tr-J) and from the Cretaceous to the Paleogene (K-Pg) periods. Both periods correlate with large igneous province volcanism and the K-Pg event is often also linked to the impact of a large extraterrestrial body with the Earth. Floral turnover is a major feature of these two events with both indicating evidence of extremely high local/regional extinction or diversity loss at low taxonomic levels such as species or genus, despite neglible loses among higher plant taxa such as families. For example, the plant megafossil record preserves an extinction of 70-90% across the K-Pg in North America and an 85% decline standing species richness is observed across the Tr-J in East Greenland. The disruptions to plant communities have been explained by a variety of mechanisms including global warming, cooling and thermal stress. Wildfires are an important component of many of Earth’s ecosystems and shifts in fire regimes have been shown to be both cause and consequence of ecological transitions. In this presentation I will assess the role that fires may have played in the ecological transitions observed across the Tr-J and K-Pg and will consider whether wildfires or changes to paleofire regime were more likely a cause or a consequence of the environmental and ecological chaos associated with these two events.